Top Document: comp.compression Frequently Asked Questions (part 1/3)
The Waterloo BragZone (http://links.uwaterloo.ca/bragzone.base.html or ftp://links.uwaterloo.ca:/pub/BragZone/ ) compares the results of various image compression schemes against a 32 element test suite. Sample images are available. The Computer Vision Home Page has many links to test images in http://www.cs.cmu.edu:80/afs/cs/project/cil/ftp/html/v-images.html A bunch of standard images (lenna, baboon, cameraman, crowd, moon etc..) used to be in ftp://eedsp.gatech.edu/database/ . The images are in 256-level grayshades (256x256 pixels, 256 "colors"). [Note: the site ipl.rpi.edu mentioned below keeps changing. Images stay there for a while then disappear. They are again available at the time of writing (27 Dec 93).] The site ipl.rpi.edu (128.113.14.50) has standard images in two directories: ftp://ipl.rpi.edu/pub/image/still/usc ftp://ipl.rpi.edu/pub/image/still/canon (The directory /pub/image/sequence was taken offline because of possible copyright problems, but has come back again. In particular, Miss America is in subdirectories of /pub/image/sequence/missa.) In each of those directories are (usually) the following directories: bgr - 24 bit blue, green, red color - 24 bit red, green, blue gray - 8 bit grayscale uniform weighted gray601 - 8 bit grayscale CCIR-601 weighted And in these directories are the actual images. For example, the popular lena image is in ftp://ipl.rpi.edu/pub/image/still/usc/bgr/lena # 24 bit BGR ftp://ipl.rpi.edu/pub/image/still/usc/gray/lena-y.ras # 8 bit gray All of the images are in Sun rasterfile format. You can use the pbm utilities to convert them to whatever format is most convenient. [pbm is available in ftp://ftp.ee.lbl.gov/pbmplus*.tar.Z ]. Questions about the ipl archive should be sent to help@ipl.rpi.edu. There are few gray-scale still images and some raw data of test results available in directory ftp://nic.funet.fi/pub/graphics/misc/test-images/ There are lots of .gif images in ftp://nic.funet.fi/pub/pics/ Medical images can be found in: ftp://decaf.stanford.edu/pub/images/medical/ ftp://eedsp.gatech.edu/database/images/wchung/medical ftp://omicron.cs.unc.edu/pub/projects/softlab/ The WWW address for the National Library of Medicine is http://www.nlm.nih.gov A list of health and medical related Internet resources is available ftp://in ftp.sura.net/pub/nic/HealthResources/medical.resources.3-94 Rodney Peck <rodney@balltown.cma.com> is interested in some method of establishing a canonical ftp database of images but does not have the resources to provide an ftp site for that database. Send suggestions to rodney@balltown.cma.com. Beware: the same image often comes in many different forms, at different resolutions, etc... The original lenna image is 512 wide, 512 high, 8 bits per pel, red, green and blue fields. Gray-scale versions of Lenna have been obtained in two different ways from the original: (1) Using the green field as a gray-scale image, and (2) Doing an RGB->YUV transformation and saving the Y component. Method (1) makes it easier to compare different people's results since everyone's version should be the same using that method. Method (2) produces a more correct image. For the curious: 'lena' or 'lenna' is a digitized Playboy centerfold, from November 1972. (Lenna is the spelling in Playboy, Lena is the Swedish spelling of the name.) Lena Soderberg (ne Sjooblom) was last reported living in her native Sweden, happily married with three kids and a job with the state liquor monopoly. In 1988, she was interviewed by some Swedish computer related publication, and she was pleasantly amused by what had happened to her picture. That was the first she knew of the use of that picture in the computer business. A scan of the original Lenna from Playboy is available at http://www.cs.cmu.edu/~chuck/lennapg/lenna.shtml The editorial in the January 1992 issue of Optical Engineering (v. 31 no. 1) details how Playboy has finally caught on to the fact that their copyright on Lena Sjooblom's photo is being widely infringed. However Wired says in http://www.wired.com/news/culture/story/4000.html "Although Playboy is notorious for cracking down on illegal uses of its images, it has decided to overlook the widespread distribution of this particular centerfold". The CCITT (ITU-T) test images are in ftp://ftp.cs.waikato.ac.nz/pub/ccitt/ and http://www.cs.waikato.ac.nz/~singlis/ccitt.html [The images in ftp://nic.funet.fi/pub/graphics/misc/test-images/ccitt*.tif are corrupted.] This set is commonly used to compare binary image compression techniques. The images are 1728x2376 pixels.
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